Upgrade-Insecure-Requests

The HTTP Upgrade-Insecure-Requests request header sends a signal to the server expressing the client's preference for an encrypted and authenticated response, and that it can successfully handle the upgrade-insecure-requests CSP directive.

Upgrade-Insecure-Requests: 1

A client's request signals to the server that it supports the upgrade mechanisms of upgrade-insecure-requests:

GET / HTTP/1.1
Host: example.com
Upgrade-Insecure-Requests: 1

The server can now redirect to a secure version of the site. A Vary header can be used so that the site isn't served by caches to clients that don't support the upgrade mechanism.

Location: https://example.com/
Vary: Upgrade-Insecure-Requests

• Content-Security-Policy
• CSP upgrade-insecure-requests directive